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Innovative Position Estimation in Wireless Sensor Networks for Efficient Location-Based Services

This work presents a novel position estimation scheme for Wireless Sensor Networks (WSNs). Unlike traditional methods requiring expensive hardware, our approach employs a distributed algorithm that minimizes power consumption and implementation costs. By utilizing ISOMAP, nodes can estimate their coordinates based on quantized distances to neighbors without relying on landmarks. This scheme facilitates efficient position-based routing and location-identifying services. Results demonstrate low failure rates and minimal angular and distance errors, making it a significant advancement for applications in environments like parks and hospitals.

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Innovative Position Estimation in Wireless Sensor Networks for Efficient Location-Based Services

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  1. Position Estimation for Wireless Sensor Networks K.-F. Simon Wong Hong Kong University of Science and Technology

  2. Outline • Introduction • Position estimation scheme • ISOMAP • Distributed Algorithm • Applications • Position-Based Routing • Location-Identifying Service • Illustrative Results • Conclusion

  3. Introduction

  4. Background • Ad hoc network • High mobility, high power nodes and moderate network size. • Wireless sensor networks (WSNs) • Low mobility, low power nodes and large size (typically more than 50 nodes). • We focus on WSNs in this work.

  5. Position Estimation in WSNs • Hot topic • Position-based routing • Route according to the node’s location instead of IDs. • Location-based services • Identify the location at which sensor reading originate. • Enclosed environment, such as car park, hospital, theme park and so on.

  6. Previous Work • Two approaches for location-identifying • Approaches based on precise measurement. • Landmark-based approaches.

  7. Approaches Based on Precise Measurement • GPS, RADAR, APS and so on. • Expensive hardware. • Power inefficient. • Good for Ad hoc networks, but not suit for WSNs.

  8. Landmarks-based Approaches • Centroid algorithm, APIT, HS/GHoST, DV-HOP and so on. • Centralized algorithm. • Usually require high powered landmarks. • Bandwidth-inefficient flooding. • Good approaches, if decentralize the algorithm, and avoid flooding.

  9. Our Contribution • No expansive hardware • Reduction in implementing cost. • Less power consumption. • Distributed Algorithm • Collects information from certain number (C) of neighbors (C = 30 in our experiment). • Each node estimates its own coordinates. • Landmark-free • Landmarks are optional.

  10. Position Estimation Scheme

  11. Quantized Distance • Measuring rough distances between one-hop neighbors by power controlling. 2 4 5 1 3 CNV • Construct close-neighbor vector (CNV) for information exchanges. • Inf • 2 • 3 • 2 Host ID Distance levels

  12. Collecting CNV • Collecting CNV to construct distance matrix.

  13. ISOMAP • Given: a matrix of quantized distance of a number of nodes • Finding: the corresponding coordinates that fits the matrix and minimize error. 0 4 inf 3 4 0 2 1 inf 2 0 3 3 1 3 0 0 0 0 3 0 4 0 6

  14. Distributed Algorithm • Clearly, centralized algorithm. • Challenging to be distributed. • Demonstrates the idea in the following slides.

  15. = bootstrap node Every node obtains its own CNV at the beginning. = normal users

  16. First iteration The bootstrap asks the C neighbors to send CNV, and runs isomap.

  17. First iteration = Coordinates computed The bootstrap sends the computed coordinates to the C neighbors. = Not computed yet

  18. Second iteration Each node collects CNV from the C closest neighbors.

  19. If there is L neighbors already computed new coordinates, perform isomap to compute its OWN coordinate. (L is typically 10 for C = 30) Second iteration

  20. The computed nodes diffuses outwards. Third iteration

  21. Finally done! Nth iteration

  22. Applications

  23. Position Based Routing • Plenty of existing algorithms. • Most of them depend on GPS. • We are not proposing a new one and only gives important location information for these algorithms. • A simple algorithm is used • Greedy forwarding.

  24. Location-based Service • Relative location in position-based routing. • Landmarks can fix the rotation/reflection • No high powered landmarks. • No landmarks flooding. • Small number (around 10).

  25. Illustrative Results

  26. Relative Coordinates

  27. Global Coordinates

  28. Routing Effect:Low Failure rate

  29. Positioning Effect:Lower Angular Error

  30. Positioning Effect:Low Distance Error

  31. Conclusion

  32. Conclusion • Presented a position estimation system in WSNs. • Focus in two applications: • Position-based routing. • Location-based services. • Simulation results are shown to illustrate the performance.

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